This invention relates generally to electrode assemblies for use in batteries and the like. More specifically, the invention relates to an electrode assembly comprised of a multilayer web rolled around a mandrel where the web is comprised of a positive electrode layer, a negative electrode layer, and separator layers separating the positive and negative electrode layers.
Many different battery designs are described in issued U.S. patents. A list of exemplary battery design patents is offered in Table 1 of U.S. Pat. No. 6,040,082. Other recent battery designs are described in U.S. Pat. Nos. 5,958,088 and 6,037,077.
Essentially all of the aforementioned battery designs are characterized by an electrode assembly housed within a battery case. The electrode assembly generally comprises a so called xe2x80x9cjelly-rollxe2x80x9d including a positive electrode strip, a negative electrode strip, and separator strips rolled around a central mandrel. Frequently, the central mandrel is removed after the roll is formed to reduce weight. The electrode assembly is preferably shaped to essentially fully occupy the interior volume within the battery case which, most typically, is either cylindrical or prismatic. A suitable electrolyte fills the interior volume around the electrode assembly.
The prior art recognizes the desirability of initially tightly winding the multilayer web and later maintaining it tightly wound. For example, U.S. Pat. No. 5,603,737 describes: xe2x80x9cA leaf spring is provided between a free end of the electrode structure and an interior wall of the housing for ensuring that the electrode structure remains tightly woundxe2x80x9d.
The present invention is directed to an improved electrode assembly for batteries and the like including a central mandrel configured to exert a resilient outward force on a multilayer web wound around the mandrel. The multilayer web includes a positive electrode layer, a negative:electrode layer, and separator layers separating the positive and negative layers. The resilient outward force acts to maintain the tightness of the web roll, thus lowering electrical resistance and enhancing battery cycle life.
A preferred mandrel in accordance with the invention is formed of sheet metal configured to define a central section having first and second resilient leaves extending therefrom. The mandrel is preferably configured in the form of an S such that the leaves fold back from the central section. The leaves preferably define substantially planar areas for bearing against an inner turn of the web roll to exert a resilient outward force thereagainst.